The neurokinin receptor (NK1R), the substance P-preferring receptor, is a novel therapeutic target for neuroAIDS. Neurokinin-1 receptor antagonists (NK1RA) have antiviral activity, positive immunomodulatory effects and neurobehavioral effects. We have demonstrated significant ex vivo anti-HIV activity in monocyte- derived macrophages of NK1RA, which include the FDA licensed drug, aprepitant. The antiviral effect is mediated, in part, through CCR5 down-regulation. Aprepitant crosses the blood-brain barrier. Aprepitant is safe in rhesus macaques, and we have an ongoing two-week blinded Phase IB clinical safety trial of aprepitant in HIV-infected humans (NCT00428519). In this new program-project application, we propose a novel series of studies which will determine the mechanism of action of NK1R. There are three interactive preclinical and clinical projects, which target the development of NK1RA therapy for neuroAIDS: 1) Cellular Mechanisms-Neurokinin-1 R Antagonists in the Brain and Immune System; 2) Immune Mechanisms-Anti- HIV Actions of Neurokinin-1 R Antagonists in Depression; and 5) Phase IB Clinical Trial of Neurokinin-1 R Antagonist-Aprepitant with ritonavir boost and direct proof of NK1R antagonism efficacy, and two Cores: A) Administration; and C) Quantitative Pharmacology and Biostatistics. The optimization of the use of NKI RA in neuroAIDS therapy is proposed and the program-project encompasses basic, translational, and clinical HIV studies of tachykinin (substance P) and NK1RA. The investigators from the Joseph Stokes, Jr. Rl, CHOP, the UPenn Schools of Medicine (Depts. of Pediatrics, Psychiatry, & Medicine) and Westat. The Philadelphia ACTU and IMPAACT CTU's, Penn-CHOP CFAR, and Penn CTSU foster the proposed interactions. These molecular, immunologic, pharmacologic, and bench-to-bedside projects address this novel therapeutic target for neuroAIDS treatment. RELEVANCE (See Instructions): An integrated pre-clinical/clinical program (IPCP) is proposed to use NK1RA as anti-HIV agents in neuroAIDS. This class of receptor antagonists crosses the blood brain barrier. This NK1RA has activity as an antiviral HIV agent that improves innate immunity (Natural Killer cells) and has positive neurobehavioral effects. NK1RA are a potential novel therapy for neuroAIDS.